Adjusting means for resistance trimmers



July 8, 1958 A. s. KHOURl ADJUSTING MEANS FOR RESISTANCE TRIMMERS FiledMarch 18. 1954 2 Sheets-Sheet l 34 INVENTOR.

ALFRED S. KHoum -4. a Map A-r'ronmsx July 8,1958 A18. KHOURI 2,842,647

I ADJUSTING MEANS FOR RESISTANCE TRIMMERS Filed March 18, 1954 2Sheets-Sheet 2 INVENTOR. ALFRED S-KHOUFM Q BY '78 66 8o 44 w. W 48 F16.\z 0 ATTORNEY United States Patent Union Inc., Milwaukee, Wis., acorporation of Delaware Application March 18, 1954, Serial No. 417,171

4 Claims. (Cl. 201-55) This invention relates to improvements inadjusting means for variable resistors, particularly such resistors asare initially adjusted to balance a circuit and then left in suchadjusted state.

Resistances of this type are described and explained in the applicationof Jack S. Kilby and Alfred S. Khouri, Serial No. 394,015 for ResistanceTrimmer. In such application a pivotally mounted rotor has its free endadjustably slidable along a resistance element on an insulating base.Such rotors are relatively small and it is difficult to make theadjustment without injuring the resistance element.

It is an object of this invention, therefore, to provide a rotor for avariable resistance which may be adjusted by use of a screw driver orlike tool.

Another object of this invention is to provide a rotor with apermanently attached knob which may be adjusted by a screw driver or thelike or by hand without fear of electrical shock, which rotor may berestricted in rotation.

The first of these objects is obtained by providing the rotor with wingshaving slots spaced to receive a screw driver bit or the like. Thesecond object is obtained by securing to the rotor an insulating knobwhich is large enough to be gripped in the fingers and manipulatedwithout fear of electrical shock, and also has on its face a toolreceiving slot. This knob may be large enough to cover the resistanceand may have a stop engaged by fingers on a mounting bracket to limitits rotation.

This invention may be best understood from the following description ofa specific embodiment when read in connection with the accompanyingdrawings, in which:

Fig. 1 is a view in front elevation of a variable resistor having arotor embodying the present invention;

Fig. 2 is an enlarged fragmentary sectional view taken on the line 2-2of Fig. 1;

Fig. 3 is a perspective view of the rotor of Figs. 1 and Fig. 4 is aview in front elevation of a resistance trimmer having a rotor embodyinga modification of the in vention;

Fig. 5 is an enlarged fragmentary sectional view taken on the line 55 ofFig. 4;

Fig. 6 is an exploded perspective view of the adjusting knob and rotorshown in Figs. 4 and 5;

Fig. 7 is a view in front elevation of a resistance trimmer rotorembodying a further modification of the invention, parts being brokenaway for sake of clarity in illustration;

Fig. 8 is a view in rear elevation of the modification viewed in Fig. 7;

Fig. 9 is a view in end elevation of the modfication viewed in Fig. 7with parts broken away and shown in section;

Fig. 10 is a view in front elevation of a plurality of resistancetrimmers like those viewed in Fig. 7 secured to 2,842,647 Patented July8, 1958 a mounting strip in accordance with the present invention;

Fig. 11 is a fragmentary view in rear elevation of the mounting stripviewed in Fig. 10; and

Fig. 12 is a sectional view taken on the line 12-12 of Fig. 10.

In the modifications shown in Figs. 1 to 6 inclusive the resistancetrimmer has an insulated base plate 10 which provides the structuralsupport. Conductors 12 and 14 are bonded to such plate and lead from theedge of such plate to a resistance element 18 in the form of a segmentof an annulus also secured to such plate. A central conductor 16 extendsfrom the edge of such plate and terminates in an enlarged circularportion which surrounds a small opening through the plate 10. In suchmodifications the rotor or slider is pivotally mounted on the plate 10by an eyelet 22 which extends through the openings in the plate 10 androtor and is peened over on the rear side of such plate. Wire leads 24are connected to the outer ends of the conductors.

In the modification shown in Figs. 1 and 3 a rotor 20 has integrallyformed thereon a pair of upstanding wings 26 provided with slots 28extending inwardly from the outer edges thereof. The wings 26 are closeenough so that both slots can be engaged by the bit of a small standardsize screw driver. The wings are far enough apart so that sutiicientrotational force may be applied to the rotor to swingably adjust it tothe desired position.

In the modification shown in Figs. 4, 5 and 6 a rotor 30 has a pair ofupstanding spaced wings 32. The opposite edges of these wings areprovided with tooth-like projections 34 designed to engage a plasticknob 36. The wings 32 like the wings 26 are far enough apart so that theneeded rotational force may be applied to the rotor for its adjustment.The knob 36 has a pair of spaced slots 38 in its bottom face whichreceive the wings 32. The length of the slots is such that when the knobis pressed on the wings 32 the teeth 34 will slightly gouge the edges ofsuch slots and frictionally retain the knob in place. The diameter ofthe knob is large enough so that it can be readily grasped by thefingers to rotate the rotor 30. It is made of an insulating plasticwhich may be molded. In appearance it is obviously an insulator andhence those concerned with the adjustment of the resistance trimmer willnot have any fear of getting an electrical shock. The knob may beprovided with a slot 40 in its outer face for the reception of a screwdriver or similar tool.

The modifications shown in Figs. 7 to 12 inclusive have an insulatingbase 42 on which is mounted a resistance element 44 with its endsconnected to conductors 46 and 48. The resistance element encircles asmall opening in the plate 42 and a central conductor 50 leads from suchopening. Terminals 51 are secured by eyelets 52 to the conductors 46, 48and 50. A conductive rotor 54 is pivotally mounted on the base 42 by atubular pivot 56 so that its free end will slide along the resistanceelement 44. The rotor 54 has a pair of upstanding spaced wings 58.

An insulating manually engageable knob 60 has slots on the lower sideinto which the wings 58 are frictionally fitted to secure the knob tothe rotor 54. The knob 60 has a skirt 62 which extends over the entirearea of the resistance 44 to protect the same from manual contact whenthe knob is being manipulated. The central part of the knob 60 may beprovided with a slot 64 for the reception of a screw driver or otherlike tool. A raised bar 66 on the skirt 62 provides an abutment forlimiting the angular movement of the rotor 54.

In order to mount the resistance trimmer to a panel or the like, thereis provided a mounting bracket 68 which has flanges 70 embracingopposite edges of the base 42 provided with edge notches 72 in which theflanges 70 are seated to provide additional gripping action. Fingers 74may be provided on one of the flanges 70 at spaced places. These fingersoverlie the skirt 62 and are in the path of the bar 66. They engage thebar. 66 and limit rotation to prevent the rotor 54 from leaving contactwith the element 44. An extension on the mounting'bracket 68 may beprovided with holes 76 by which it may bereadily fastened to a chassisor the 'ke.

In the modification shown in Figs. l0, l1 and 12, the resistancetrimmers are identical with'that show in'Figs. 7, 8 and 9, however, themounting bracket is formed so that a plurality of such trimmers may bemounted on one bracket and handled as a unit. The mounting bracket 78consists of an elongated strip of metal. At proper spacing along itslength there are flanges 80 which are formed up from the body of thebracket from under the plate 42. One of the flanges 80 may be providedwith spaced fingers 82. The blanking shape for this flange 80 and 7 itsfingers is indicated at 84 (Fig. 11). It may be desirable to providealong the bottom edge of the bracket 78 a channel-like reinforcingmember 86 which will stifien the mounting bracket 74 and also providefurther engagement for the resistance trimmers. To assemble a resistancetrimmer to the mounting bracket it is placed on the bracket after theflanges 72 have been pressed to a vertical position. Thereafter theupper ends of the flanges are formed over the base plate 42 asindicated. The mounting plate with its multiplicity of resistancetrimmers maybe secured to a panel or chassis in the usual manner.

What I claim and desire to secure by this patent is:

1. 'In a resistance trimmer having an insulating supporting plate and aresistance element fixedly mounted thereon, a flat conductive rotorpivotally mounted to said plate and having wiping engagement with saidresistance, said rotor having an opening therethrough, a pivot extendingfrom said plate through said opening to only the outerside of saidrotor, said rotor having a pair of wings integral therewith andextending outwardly of said plate, said wings being diametricallypositioned with respect to the center of said opening and provided withteeth extending from the sides thereof, a molded insulating knob havinga 4 spaced slots adapted to receive said wings with the edges of saidslots frictionally engaged by said teeth, said knob being rigidlymounted on said rotor with said wings inserted in said slots.

2. In a resistance trimmer having an insulating supporting plate with aresistance element on a side thereof, a conductive rotor independentlypivotally mounted to said plate on said side, knob holding meansintegral with said rotor,'and an insulating knob mounted on said meansand carriedthereby independent of the pivotal mounting of said rotor,said knob having a'skirt covering said resistance element and spacedtherefrom whereby said resistance element is protected during manualmanipulation of said knob.

3. The combination as claimed in claim 2, in which said skirt has araised abutment thereon and in which there is a second abutment securedto said supporting plate and overlying said skirt to engage said firstabutment and limit the rotation of said knob.

4. A resistance trimmer having an insulating supporting plate, aresistance element on a side of said plate, a-conductive rotor mountedon said side of said plate for movement along said resistance element,an insulating knob secured tosaid rotor and carried therebyindependently of the mounting of said rotor, said knob covering saidresistance element, and a mounting bracket for said resistance trimmerhaving flanges engaging said supporting plate from opposite sides, oneof said flanges having a finger overlying said rotor, said rotor havingan abutment raised therefrom engageable with said finger to limit therotation of said rotor.

References Cited in the file of this patent UNITED STATES PATENTSArisman Oct. 18, 1955

